The present invention relates to a twist lock, to be disposed between two containers, for connecting the containers loaded or stored on top of each other in multiple tiers in a container yard or on a containership.
As illustrated in FIG. 11, containers Ct are generally loaded and unloaded between a container yard Yd and a containership Sh.
By way of example, for the loading of a container Ct, a container Ct stored at the container yard Yd is first loaded on a container vehicle V such as a trailer by means of a transfer crane Tc or a straddle carrier and then carried to the apron Ap. A container Ct at the apron Ap is lifted by a spreader Sp of a container crane Cr and rested on another container Ct on the deck of a containership Sh.
As for the unloading of a container Ct from the deck of a containership Sh, a container Ct is lifted and transferred to the apron Ap by means of the spreader Sp of the container crane Cr. The container Ct is then loaded on the container vehicle V, and carried from the apron Ap to the container yard Yd.
When containers Ct are loaded or stored in multiple tiers in a container yard Yd or on a S containership Sp, an upper container Ct and a lower container Ct are connected with each other to prevent them from falling off. As the connection means, container locks are disposed, via fitting parts, between the four bottom corners of the upper container and the four top corners of the lower container.
An example of such container locks is disclosed in International Publication No. WO92/05093 as twist lock.
The twist lock 100 is described, referring to FIGS. 12 to 15.
The twist lock 100 comprises a housing 101 composed of a right housing component and a left housing component integrally joined by a bolt, a spindle 102 (FIG. 15) rotatably held in the housing 101, and an upper twist lock cone 103 and a lower twist lock cone 104 which are integrally connected to the upper end and the lower end of the spindle 102, respectively.
The housing 101 includes an upper raised part 101U and a lower raised part 101D integrally incorporated on the upper and lower portions. The upper and lower raised parts 101U, 101D are designed in a shape which matches a fitting hole Fa of a corner fitting F mounted on the container Ct (FIG. 18), and capable of fitting into a fitting hole Fa formed in a bottom corner fitting F of an upper container Ct and a fitting hole Fa formed in a top corner fitting F of a lower container Ct, respectively.
The housing 101 further includes a through-hole (not shown) which extends through the upper raised part 101U and the lower raised part 101D, and which supports the spindle 102.
The corner fitting F having the fitting hole Fa to be mounted on a container Ct is not specifically illustrated herein. For their specification, reference can be made to JIS Z1616.
The upper twist lock cone 103 and the lower twist lock cone 104 are designed to match the shape of the fitting hole Fa in the corner fitting F of the container Ct, and engageable with the fitting hole Fa. In association with the rotation of the spindle 102, the upper and lower twist lock cones 103, 104 rotate on the top surface of the upper raised part 101U and the bottom surface of the lower raised part 101D, respectively. When the upper twist lock cone 103 is detachable with respect to the fitting hole Fa in the bottom corner fitting F of the upper container Ct, the lower twist lock cone 104 is engaged with the fitting hole Fa in the top corner fitting F of the lower container Ct. On the other hand, when the lower twist lock cone 104 is detachable with respect to the fitting hole Fa in the top corner fitting F of the lower container Ct, the upper twist lock cone 103 integrally connected to the spindle 102 is engageable with the fitting hole Fa in the bottom corner fitting F of the upper container Ct, in which case a top view of the twist lock shows the spindle 103 crossing over the fitting hole Fa in the form of the letter X.
The lower twist lock cone 104 is shaped such that it is imparted with a rotating force when pressed against the fitting hole Fa in the corner fitting F, provided that the lower cone 104 is in an engaging position with respect to the fitting hole Fa. To be more specific, the lower twist lock cone 104 is engageable with the fitting hole Fa in the corner fitting F, when the spindle 102 stays at the first position A to be described below. Under this condition, by pressing the lower twist lock cone 104 against the edge of the fitting hole Fa in the corner fitting F, a pressurising force is imposed on the corner fitting F through the lower twist lock cone 104, whereas the lower twist lock cone 104 receives a reactive force in return. Owing to the reactive force acting on the lower twist lock cone 104, a properly shaped lower twist lock cone 104 is forced to rotate around the rotation axis of the spindle 102.
As shown in FIG. 15, a cavity 101X is formed inside the housing 101, and provided with a first stop element 101a and a second stop element 101b which can be contacted by a stop arm 1021 securely integrated with the spindle 102. In this structure, the spindle 102 is capable of rotating between the first position A and the third position C where the stop arm 1021 contacts the first stop element 101a and the second stop element 101b in the cavity 101X, respectively.
Normally, the spindle 102 is urged by a torsion spring 105, whereby the stop arm 1021 stays in contact with the first stop element 101a in the cavity 101X. Further, a wire 106 is disposed along a groove 1022 formed in the circumference of the spindle 102. One end of the wire 106 is looped around the stop arm 1021, while the other end is drawn out through a nozzle 107 and fixed to a handle 108. Of the nozzle 107, the right and left edge portions are slidably fitted in a transverse slot 101Y, and the upper and lower portions are provided with slots 107a, 107c, respectively. Further, a stop element 1061 is provided in the vicinity of the handle-side end of the wire 106. The stop element 1061 is capable of checking selectively at the slot 107a or 107c. 
The nozzle 107 is displaceable along the transverse slot 101Y in which the right and left edge portions thereof are fitted. The nozzle 107 is usually urged into contact with one end of the transverse slot 101Y by means of a spring 109 arranges within the housing 101.
With the use of the above twist lock 100, two vertically loaded containers Ct are joined in the following manner. First, a container Ct in a container yard Yd is loaded on a container vehicle V using a transfer crane Tc and carried to an apron Ap. Then, in the apron Ap, the container Ct is lifted by a spreader Sp of a container crane Cr and suspended approximately one meter above the ground, where the upper twist lock cone 103 of the twist lock 100 is mounted to every bottom corner fitting F of the container Ct (FIG. 16). Specifically, the handle 108 is pulled by hand in order to check the stop element 1061 of the wire 106 at the slot 107a of the nozzle 107. At this first checking position, the spindle 102 is rotated to the third position C where the stop arm 1021 contacts the second stop element 101b in the cavity 101X, while the upper twist lock cone 103 comes in agreement with the upper raised part 101U of the housing 101, as seen from above. Thereby, the upper twist lock cone 103 can be inserted together with the upper raised part 101U into the fitting hole Fa in the bottom corner fitting F of the upper container Ct. Once the upper twist lock cone 103 is inserted into the fitting hole Fa, the handle 108 is pulled by hand again so as to release the stop element 1061 of the wire 106 from the slot 107a of the nozzle 107. On the release of the stop element 1061, the torsion spring 105 urges the spindle 102 back to the first position A where the stop arm 1021 contacts the first stop element 101a in the cavity 101X. At the first position A, the upper and lower twist lock cones 103, 104 are both engaged with the fitting holes Fa in the corner fittings F, as mentioned above, whereby the twist lock 100 does not fall off or come out from the corner fitting F of the container Ct (FIG. 17).
After the twist locks 100 are mounted on the bottom corner fittings F, the container Ct is lifted by a container crane Cr and transferred onto another container Ct on the deck of a containership Sh (FIG. 18). While the container Ct is being rested, the lower twist lock cone 104 of each twist lock 100 is forced to rotate along the edge of the fitting hole Fa in a corresponding top corner fitting F of the lower container Ct, against the urging force deriving from the torsion spring 105. When the lower twist lock cone 104 is rotated into agreement with the lower raised part 101D of the housing 101 as seen from above, the lower twist lock cone 104 and the lower raised part 101D enter the fitting hole Fa in the top corner fitting F of the lower container Ct. Having entered the top corner fitting F, the lower twist lock cone 104 returns to the engaging position due to the urging force of the torsion spring 105 and engages with the fitting hole Fa. Upon the engagement, the upper and lower containers Ct are joined by the twist locks 100, wherein the upper and lower twist lock cones 103, 104 are engaged with the bottom corner fittings F of the upper container Ct and the top corner fittings F of the lower container Ct, respectively (FIG. 19).
Now, the container Ct loaded on the deck of the containership Sh is unloaded in the following process. With the lower twist lock cone 104 locating at the engaging position, the handle 108 is pulled down or pushed down on the deck so as to check the stop element 1061 at the slot 107c. At this second checking position, the spindle 102 and the stop arm 1021 locate at the second position B between the first stop element 101a and the second stop element 101b in the cavity 101X of the housing 101. At the second position B, the lower twist lock cone 104 positionally corresponds to the lower raised part 101D of the housing 101 as seen from above, and can be thus removed from the fitting hole Fa in the top corner fitting F of the lower container Ct (FIG. 20).
Following the release of the lower twist lock cone 104, the container Ct is transferred by the spreader Sp of the container crane Cr, and then suspended approximately one meter above the ground at the apron Ap, where the upper twist lock cone 103 is removed from each bottom corner fitting F of the container Ct. Specifically, the handle 108 is pulled by hand to check the stop element 1061 of the wire 106 at the slot 107a of the nozzle 107. At this first checking position, the spindle 102 is rotated to the third rotation position C where the stop arm 1021 contacts the second stop element 101b in the cavity 101X, while the upper twist lock cone 103 comes in positional agreement with the upper raised part 101U of the housing 101 as seen from above. Therefore, the twist lock 100 can be removed from the fitting hole Fa in the bottom corner fitting F of the container Ct (FIG. 21). Thereafter, the container Ct at the apron Ap is loaded onto the container vehicle V by the container crane Cr and transported to the container yard Yd.
The above-mentioned conventional twist lock has facilitated the loading and joining of containers. In the loading of containers, the twist lock is attached to a bottom corner fitting of a container to be loaded. By resting this container on another container, the lower twist lock cone enters a top corner fitting of the lower container, with rotating along the edge of the fitting hole in the corner fitting. Upon the entry, the lower cone automatically returns to the position engaging with the corner fitting as urged by a torsion spring. Eventually, the upper and lower containers are joined together. On the other hand, in the unloading of the containers, the spindle (i.e. the lower twist lock cone) needs to be rotated from the engaging position to the releasable position against the urging force of the torsion spring, in which case the rotation should be effected by manual operation of the handle. In order to check the stop element of the wire at the slot of the nozzle, a dockworker has to pull down or push down the handle with the use of a long actuator pole, on the top of the multiple tiers of containers, or on the deck (in a containership) or the ground (in a container yard) as shown in FIG. 20. Such an unlocking process not only requires a long working time but also imposes a substantial physical burden to dockworkers. It is obviously difficult and exhausting to operate the handle with the tip of a long and heavy actuator pole. In addition, the twist lock of prior art is undesirable in the safety aspect, because operation on the top-tier containers inevitably involves the risks of falling off therefrom and other accidents.
In order to solve these problems, the present invention intends to provide a twist lock for connecting containers which enables the automatic connection and the automatic disconnection between an upper container and a lower container, without any high-place operations or the like.
According to the first embodiment of the present invention, a twist lock for connecting containers comprises a housing integrally including an upper fitting part and a lower fitting part each being capable of fitting into a fitting hole in a corner fitting of a container and being formed with a through-hole which extends through the upper and lower fitting parts, a spindle inserted in the through-hole in a rotatable and vertically displaceable manner, an upper lock connected to the top end of the spindle and being engageable with the fitting hole in the corner fitting of the container, and a lower lock being in positional agreement with and fixed securely to the lower fitting part of the housing and slidably fitted with a plurality of locking members which can engage with and disengage from the fitting hole in the corner fitting of the container. In this twist lock, the spindle is urged by a spring member in such a direction that the upper lock can engage with the fitting hole in the corner fitting of the container, while each of the locking members is urged by another spring member in such a direction that each locking member can retract into the lower lock. When the spindle locates at a lowered position, the locking members contact the spindle and project from the lower lock against the urging force of the spring means, thereby engaging with the fitting hole in the corner fitting of the container to prevent the release of the lower lock. When the spindle locates at a raised position, the locking members lose contact with the spindle and retract into the lower lock by the urging force of the spring means, thereby disengaging from the fitting hole in the corner fitting of the container to permit the release of the lower lock.
For the loading of a container, the twist lock of the first embodiment is attached to a container by mounting the upper lock into a fitting hole in a bottom corner fitting of the container. While the housing descends relative to the spindle due to its own weight, the locking members lose contact with the spindle and retract into the lower lock. As a result, the lower lock can be introduced into a fitting hole in a top corner fitting of another container. When the container is transferred onto the lower container, the spindle descends relative to the housing. As the spindle contacts and pushes out the locking members, they are engaged with the fitting hole in the top corner fitting of the lower container to connect the upper and lower containers.
Unloading of the container is performed simply by lifting the container. Thereby, the spindle is raised, relative to the housing, by the upper lock engaging with the fitting hole in the bottom corner fitting of the upper container. The locking members thus lose contact with the spindle and retract into the lower lock. Consequently, the locking members are disengaged from the fitting hole in the top corner fitting of the lower container, from which the lower lock can come out.
As described above, when a container mounted with the twist lock at the fitting hole in every bottom corner fitting is rested onto another container, the lower lock is fitted into the fitting hole in the top corner fitting of the lower container, and the locking members are engaged therewith. Likewise, simply by lifting the container, the locking members are disengaged from the fitting hole in the top corner fitting of the lower container. Thus, the twist lock of the present invention enables not only automatic connection between the upper and lower containers in loading, but also automatic disconnection between the twist lock and the lower container in unloading. This advantage eases the workload and provides safe working environments, as the dockworkers no longer have to work on the top of multiple-tier containers or to operate a working tool.
In a preferable structure of the above twist lock, the spindle is linked with a stop handle through a linking member, and the housing includes a stop for checking the stop handle.
According to this structure, the stop handle connected to the linking member is manually pulled and checked at the stop in the housing. Thereby, the spindle is rotated against the urging force of the spring means, allowing the upper lock fixed to the spindle to rotate to and remain at a position where the upper lock can be freely inserted into or removed from the fitting hole in the corner fitting of the container. Therefore, even if the twist lock may be broken, at least the upper container can be disconnected from the twist lock as an emergency measure.
In another preferable structure, a fitting groove is formed in the outer circumferential surface of the spindle, and at least one connecting bore is provided in the right and left components of the housing, respectively. Each connecting bore is formed in a predetermined length in the direction extending from a radius of the through-hole, and has an open end at a position facing the fitting groove in the spindle at the lowered position. At least one ball is rotatably accommodated in each connecting bore.
According to this structure, when the vertically connected containers are inclined, the ball rolls along one of the connecting bores corresponding to the inclined direction of the housing. Thus, the ball is to fit into the fitting groove in the spindle at the lowered position. Consequently, the spindle can bear the lift-up force resulting from the jump of the containers and transmitted via the upper lock. The connection between the upper and lower containers is thus maintained.
In still another preferable structure, a fitting groove is formed in the inner circumferential surface of the housing, and at least one connecting bore is provided in the right and left portions of the spindle, respectively. Each connecting bore extends in a radius direction of the through-hole and communicates with each other at the centre. Further, each connecting bore has an open end at a position facing the fitting groove in the housing, provided that the spindle locates at the lowered position and the upper lock is engaged with the fitting hole in the corner fitting of the container. At least one ball is rotatably accommodated in the connecting bores.
According to this structure, when the vertically connected containers are inclined, the ball rolls along one of the connecting bores corresponding to the inclined direction of the spindle at the lowered position. Thus, the ball is to fit into the fitting groove in the housing. Consequently, the spindle can bear the lift-up force resulting from the jump of the containers and transmitted via the upper lock. The connection between the upper and lower containers is thus maintained.
Preferably, each connecting bore in the above structures is inclined, by a predetermined downward gradient, from the open end facing the fitting groove formed in the spindle or the housing down to the direction in which the connecting bore extends.
Due to the gradient, when the containers stay level, each ball rolls down to the bottom end of the connecting bore and does not interfere with the fitting groove in the spindle. Therefore, this arrangement permits the upward movement of the spindle, except when the inclination of the containers exceeds the gradient of the connecting bore, while effectively preventing the accidental locking of the spindle in unloading the containers.
In a further preferable structure, a fitting groove is formed in the outer circumferential surface of the spindle, and at least one connecting bore is provided in the right and left components of the housing, respectively. Each connecting bore is formed in a predetermined length in the direction extending from a radius of the through-hole, and has an open end at a position facing the fitting groove in the spindle at the lowered position. In addition, each connecting bore accommodates a plurality of balls in a rotatable manner. The housing further includes a pair of fitting bores vertically formed on the right and left sides of the upper fitting part along a concentric circle of the through-hole, with the bottom end of each fitting bore communicating with the connecting bore. A guide is inserted in each fitting bore in a vertically slidable manner and urged by a spring means to project slowly from the top surface of the housing. Accordingly, an inner ball is allowed to fit in the fitting groove in the spindle when the guide locates at a lowered position, and allowed to roll out of the fitting groove when the guide locates at a raised position.
According to this structure, when the bottom corner fitting of the upper container is rested on the twist lock, the guides are pressed down against the urging force of the spring means. In connection with the descent of the guides, the inner balls are allowed to fit in the fitting groove in the spindle to block the upward movement of the spindle. On the other hand, when the upper container is lifted up, the guides project from the top surface of the housing by the urging force of the spring means. In connection with the rise of the guides, the inner balls roll out of the fitting groove in the spindle to permit the upward movement of the spindle. Even if the vertically connected containers are shaken violently due to high waves in the sea or the like, the rising rate of the guides is not affected by the sudden jump of the containers, so that the balls remain fitted in the fitting groove in the spindle for a certain period of time. As a result, even when the spindle is subjected to the lift-up force transmitted via the upper lock, this twist lock keeps the connection between the upper and lower containers, with preventing the upward movement of the spindle.
Preferably, the connecting bore in the above structure is inclined, by a predetermined downward gradient, from the open end facing the fitting groove in the spindle down to the other end communicating with the fitting bore.
Due to the gradient, when the containers stay level, each ball rolls down to the bottom end of the connecting bore and does not interfere with the fitting groove in the spindle. This arrangement permits the upward movement of the spindle, except when the inclination of the containers exceeds the gradient of the connecting bore, while effectively preventing the accidental locking of the spindle in unloading the containers.